Inserted blade cutter



Aug. 30, 1938. F. P. MILLER 5 INSER'TED BLADE CUTTER 5 Filed Sept. 10,1936 12 r F/a.

w W? M P/rcH Aw: or 7' P4541454 75 U A l I I I ATTORNEY Patented Aug.30, 1938 UNITED STATES PATENT OFFICE 11 Claims.

My invention relates to cutting tools of the inserted blade type andmore particularly to an improved means to secure the blades in the toolbody.

This invention has particular reference to tools of the type disclosedin prior Patent No. 1,951,100

issued to J. A. Spohr and myself, more partic- I ,ularly to theconstruction shown in Figures 11 and 12 of said patent, and is animprovement in the means for locking the blade in the body of the tool.

In the tools of the prior art difficulty has been encountered inobtaining the desired wedging angle between the blade and locking memberand in obtaining the necessary bearing contact between the lockingmember and the body of the tool. An important object of the presentinvention is to provide a locking member of this character which willhave an increased wedging angle with respect to the blade of the tooland which will have an increased bearing surface contact with the bodyof the tool.

Another object of my present invention is to provide a device of thischaracter which will effectively secure the cutting blade to the toolagainst the stress and strain of use without impairing the action of thethreads.

A further object of this invention is to provide an improved method offorming the locking member and its socket to produce the desired wedgingangle without increasing the angle at which the locking member istapered.

Still another object of my invention is to provide a device of thischaracter which is inexpensive to manufacture, simple in constructionand operation and which will have a long life.

Other objects and advantages of my invention will be apparent during thecourse of the following description.

In the accompanying drawing which, forms a part of this specificationand wherein like characters of reference denote like parts throughout,

Figure 1 is a perspective view of a tool embodying my invention, one ofthe blades of which is broken away,

Figure 2 is a plan view of the locking member and adjacent portions ofthe blade and tool body, and,

Figure 3 is a sectional view taken on the line 3-3 of Figure 2.

In the drawing, wherein for the purpose of illustration is shown apreferred embodiment of the invention, the numeral l designates the bodyof a tool such as a reamer, counterbore,

milling cutter, boring head, facing tool or the like which is providedwith a series of circumierentially spaced, longitudinally extendingslots ll opening out through the periphery thereof and which receive thecutting blades l2. In the form of the invention illustrated, the rearends of the blades are beveled and are engaged by a conventional form ofthreaded adjusting collar H! which is locked in position on the threadedportion l3 of the tool body by a lock collar lfir in The collars l4 andi5 prevent rearward movement of the blades IZunder the thrust of thecutting action and provide means for adjusting the blades quickly anduniformly.

It has been proposed to lock the blades l2 in position in the tool bodyby means of cylindrical threaded bores breaking into the blade slots IIand receiving tapered threaded plugs or screws which are wedged againstthe blades. In one instance, for example as shown in Figures 11 and 12of the aforementioned patent, the wedging screw was tapered on the topsof the threads in a manner similar to the screw in this application, butthe socket which received the screw was tapped or threaded in theconventional manner and the screw and socket engaged each other on theirpitch lines only. In order to obtain a sufficient wedging angle, it wasnecessary to remove the greater part of the threads adjacent the leadingend of the screw, destroying I now propose to so form the locking screw0 and bore that a greatly increased wedging angle will be obtained andat the same time the bearing surface between the screw and socket willbe increased, and an even greater bearing surface provided adjacent theleading end of the screw than at the rear end thereof.

The bores or sockets it are arranged generally radially of the tool bodyl0 and their axes are arranged at a slight angle to the surfaces of theblades, as indicated at C in Figure 3, and this angle is preferably from3 to 5 although any desired angle may be employed. The socket isproduced bya drill arranged with its axis at a slight angle to the bladel2, this angle being the same as angle C, the axis of the drill and theplane, of the blade converging inwardly. The drill pro' duces acylindrical bore the sides of which are parallel. The next operation isperformed with the conventional form of straight tap, the pitch line ofwhich is parallel to the axis of the tap.

However, such taps are provided with the conventional taper lead tofacilitate starting and operation of the tap, and this taper isrepresented by angle D in Figure 3 which is the same as angle C. The tapis fed into the drilled opening to a depth approximately the length ofthe tapered tap lead, and produces tapered thread grooves of uniformpitch, the bottoms of the grooves diametrically opposite the bladeforming a bearing surface for the tops of the screw threads, thisbearing surface being inclined to the surface of the blade at an angleequal to C plus D, which is identical to the included angle of the taperformed on the tops of the screw threads. By reference to Figure 3 itwill be seen that the tapped bore has a species of tapered thread,although the pitch line of the threads is parallel to the axis of thebore and of the tap. Otherwise expressed, the threaded bore is onlytapered when the line of the bottom of the threads is considered inrelation to the axis of the bore or recess. A line through the apices ofthe threads, however, is parallel to the axis of the bore. It will beseen that the taper of the tap lead, being produced by grinding away thetops of the threads on the tap produces grooves or threads in the borehaving flat surfaces at their bottoms which increase in area approachingthe inner end of the bore.

The screw ll that is inserted in the bore i6 is of slightly lessdiameter than the bore to cause wedging of the screw against the bladeinstead of seating itself in the bore. The screw ll is first formed as astraight screw with the pitch line of its threads parallel to its axis.Tapering is then produced by turning or grinding off the tops of thethreads in increasing amounts as the leading end of the screw isapproached to produce a taper on the tops of the screw threadscorresponding to the taper of the tap used to produce the threads of thebore I6.

Referring to Figure 3 it will be seen that the threads of the screw andsocket do not bear on the pitch line as is customary, but the taperedtops of the threads on the screw bear on the flattened taper surface atthe bottoms of the threads in the socket. To insure a bearing contact atthis point the threads of the screw are cut somewhat deeper than thethreads of the socket and a slight clearance i8 is consequently producedbetween the threads of screw and socket. The screw may be rotated by awrench or other implement engaging recess l 9 in the top of the screw.

With this construction the effective wedging angle is the sum of anglesC and D whereas in former constructions the effective angle is C only.By the construction shown, therefore, the effective wedging angle isdoubled, the bearing surface between screw and socket is greatlyincreased and a positive locking engagement of the screw and bladeresults. Doubling the effective wedging angle also permits more generoustolerances in machining the blade slot, the blade, the socket, and thescrew, because the screw moves laterally toward the blade twice as farwith the same amount of axial travel and thus quickly offsets machininginaccuracies and simplifies the assembling of these parts into theirproper relationship.

It will be noted that the screw ll bears at diametrically oppositepoints on the blade I2 and socket 56. An important feature of thepresent invention is the bearing contact of the tapered tops of thethreads of the screw and the flattened bottoms of the socket threads. Byreference to Figure 3 it will be seen that these bearing surfacesincrease progressively approaching the leading end of the screw and theinner end of the socket. As a consequence, the improved constructionprovides double the effective wedging angle and greatly increases thebearing surface. This is in direct contrast to the former constructionin which the desired wedging angle resulted in the cutting away ofsubstantially the entire thread toward the leading end of the screw,destroying the bearing surface between the threads of the screw andsocket. In the present construction the increased bearing surfacetowards the leading end of the screw is attributable to the fact thatthe bearing is on the top of the thread of the screw and not on thepitch line as formerly.

It will be seen that I have provided a simple and inexpensiveconstruction in which a powerful wedging or looking pressure is broughtto bear on the blade by the increased wedging angle provided, and inwhich this pressure is maintained due to the increased bearing surfacebetween the threads of the screw and socket.

While I have shown and described the preferred embodiment of myinvention it is to be understood that various changes in the size, shapeand arrangement of parts may be resorted to without departing from thespirit of my invention or the scope of the subjoined claims.

Having thus described the invention, what is claimed is:

1. In an inserted blade cutter, a body having a slot and a socketbreaking into the slot, a blade in the slot, the axis of the socketbeing at an I angle to the plane of the blade, said socket having athread tapering to the inner end thereof, the pitch line of said threadbeing parallel to the axis of the socket, and a screw adapted to bereceived in said socket to engage the blade, said screw having a threadtapered toward its leading end, the pitch line of the thread of thescrew being parallel to the axis of the screw, said screw having adiameter sufficiently less than the diameter of the socket to movelaterally therein, whereby the screw contacts the blade and socket atdiametrically opposite points on the periphery of the screw.

2. In an inserted blade cutter, a body having a slot therein, a blade insaid slot, said body having a socket breaking into the slot, the axis ofthe socket being arranged at an angle to the plane of the blade, saidsocket having a thread of progressively diminishing depth toward theinner end of the socket, and a screw adapted to be received in thesocket and having a thread of progressively diminishing depth toward theleading end of the screw, the threads of the screw and socket having auniform pitch, and the tops of the threads on the screw being adapted tohave a bearing contact with the bottoms of the socket threads on oneside of the socket.

3. In an inserted blade cutter, a body having a slot therein, a blade insaid slot, said body having a socket breaking into the slot, the axis ofthe socket being arranged at an angle to the plane of the blade, saidsocket having a thread .of progressively diminishing depth toward theinner end of the socket, and a screw adapted to be received in thesocket and having a thread of progressively diminishing depth toward theleading end of the screw, said screw having a diameter sufficiently lessthan the diameter of the socket to move laterally therein whereby thescrew contacts the blade and socket at diametri-,

cally opposite points on the periphery of the screw.

4. In an inserted blade cutter, a body having a slot therein, a blade insaid slot, said body having a socket breaking into the slot, the axis ofthe socket being arranged at an angle to the plane of the blade, saidsocket having a thread of uniform pitch and progressively diminishingdepth toward the inner end of the socket, and a screw adapted to bereceived in the socket and having a thread of uniform pitch andprogressively diminishing depth toward its leading end, said screw beingforced against the blade by an effective wedging angle equal to the sumof the angle between the axis of the socket and the face of the bladeand the angle between the axis of the socket and a line connecting thebottoms of the socket threads, said screw having a diameter sufficientlyless than the diameter of the socket to move laterally therein, wherebythe screw contacts the blade and socket at diametrically opposite pointson the periphery of the screw.

5. In an inserted blade cutter, a body having a slot therein, a blade insaid slot, said body having a socket breaking into the slot, the axis ofthe socket being at an angle to the plane of the blade, said sockethaving a thread of progressively diminishing depth toward the inner endof .the socket, and a screw adapted to be received in the socket andhaving a thread of progressively diminishing depth toward the leadingend of the screw, the threads of the screw and socket having parallelpitch lines, and the tops of the threads on the screw being adapted tohave a bearing contact with the bottoms of the socket threads on oneside of the socket, whereby the bearing surface between the screw andsocket threads increases progressively towards the leading end of thescrew.

6. In an inserted blade cutter, a body having a slot therein, a blade insaid slot, said body having a socket breaking into the slot, the axis ofthe socket being at an angle to the plane of the blade, said sockethaving a thread of progressively diminishing depth toward the inner endof the socket, and a screw adapted to be received in the socket andhaving a thread of progressively diminishing depth toward the leadingend of the screw, the threads of the screw and socket having parallelpitch lines, the tops of the threads on the screw being adapted to havea bearing contact with the bottoms of the socket threads on one side ofthe socket, whereby the bearing surface between the screw and socketthreads increases progressively towards the leading end of the screw,and said screw having a diameter sufiiciently less than the diameter ofthe socket to move laterally therein, whereby the screw contacts theblade and socket at diametrically opposite points on the periphery ofthe screw.

7. In an inserted blade cutter, a body having a slot therein, a blade insaid slot, said body having a socket breaking into the slot, the axis ofthe socket being at an angle to the plane of the blade, said sockethaving a thread of progressively diminishing depth approaching its innerend, and a screw adapted to be received in the socket and having athread the top of which is cut away in progressively increasing amountstowards the leading end of the screw.

8. In an inserted blade cutter, a body having a slot therein, a blade insaid slot, said body having a socket breaking into the slot, the axis ofthe socket being at an angle to the plane of the blade, said sockethaving a thread of progressively diminishing depth approaching its innerend, and a screw adapted to be received in the socket and having a.thread the top of which is cut away in progressively increasing amountstoward the leading end of the screw, the threads of the socket and screwhaving parallel pitch lines, and the cut away tops of the threads on thescrew being adapted to have a bearing contact with the bottoms of thesocket threads on one side of the socket.

9. In an inserted blade cutter, a body having a slot therein, a blade insaid slot, said body having a socket breaking into the slot, the axis ofthe socket being arranged at an angle to the plane of the blade, saidsocket having a thread of progressively diminishing depth approachingits inner end, and a screw adapted to be received in the socket andhaving a thread the top of which is cut away in progressively increasingamounts toward the leading end of the screw, said screw having adiameter sufiiciently less than the diameter of the socket to movelaterally therein whereby the screw contacts the blade and socket atdiametrically opposed points on the periphery of the screw.

10. In an inserted blade cutter, a body having a slot therein, a bladearranged in the slot, said body having a socket breaking into the slotfor the full length of the socket, the axis of the socket being disposedat an angle to the plane of the blade, and a screw received in saidsocket, the screw and socket having threads of uniform pitch andprogressively diminishing depth toward their inner ends, the threads ofthe screw having a slightly greater depth than the corresponding threadsof the socket, whereby the tops of the threads of the screw bear againstthe bottoms of the threads of the socket.

11. In an inserted blade cutter, a body having a slot and a socketbreaking into the slot, a blade in the slot, the axis of the socketbeing arranged at an angle to the plane of the blade, said socket beingprovided with a thread tapering to the inner end thereof, the pitch lineof said thread being parallel to the axis of the socket, and a screwadapted to be received in said socket to engage the blade, said screwhaving a thread tapered toward its leading end, the pitch line of thethread of the screw being parallel to the axis of the screw.

FRANK P. MILLER.

